This invention relates to a method and apparatus for creating seismic vibrations.
Seismic mapping can be conducted by vibrating the earth in a region to be mapped. One method of vibrating the earth involves the detonation of an explosive such as dynamite, which produces only a single shock. Vibrations at a desired frequency can be produced by a Vibroseis system which includes eccentic weights that are rotated and attached to a heavy platform which is placed on the ground. This system has the advantage that it is relatively safe and enables the production of vibrations of a desired frequency. However, it also has disadvantages in that it involves large capital cost, requires large amounts of power to operate, produces a relatively weak signal such as 10 psi at the vibrator, and is limited to low frequencies of between a few Hz and about 150 Hz. A system which was relatively inexpensive to set up and operate, which was relatively safe, and which produced vibrations of a desired frequency and of considerable magnitude would facilitate the conducting of seismic mapping.